The following background information is provided to assist the reader to understand the environment in which the invention will typically be used. The terms used herein are not intended to be limited to any particular narrow interpretation unless specifically stated otherwise in this document.
It is well known that pressure activated switches have been used in a variety of safety and equipment control applications. For example, U.S. Pat. No. 4,088,856 entitled “Perimeter Safety Switch Mounted To Support Disposed Remote From The Machine Body” teaches a perimeter safety switch, commonly known as a tape switch, that is accessible from any point of operation of the machine, and which can be actuated other than with the operator's hands. More specifically, the perimeter safety switch comprises a continuous longitudinal switch capable of being actuated at any point over its length, which is mounted on a bracket extending around the periphery of the machine, or at least around all areas which are accessible to the operator. If the operator is injured, either the operator himself or a co-worker can immediately stop the machine by a hand, leg or lower torso without searching for a switch which is remote or inaccessible, thus reducing the possibility of further injury and panic.
In another example, U.S. Pat. No. 4,995,639 entitled “Vehicle Crush Zone Crash Sensor” teaches a tape or ribbon switch technology as a crash switch used to sense and initiate deployment of an air bag passive restraint system. The sensor is responsive to trigger the passive restraint system when the vehicle impacts with a barrier which causes vehicle elements in the crush zone to deform as far back as the sensor position.
Pressure activated switches are also used for opening of doors in a transit vehicle. They are typically affixed along the leading edge of the door panel and are easily accessible to the passenger's hands, arms, and upper torso. In such application, the driver of the transit vehicle remotely unlocks but does not open the door, which is considered as enabled for opening. At the same time either a light above the door or the switch will illuminate which will be interpreted by a passenger that a closed door can be now opened by activating the switch. It is preferable to illuminate the switch itself since use of the external light carries additional material and installation labor costs.
U.S. Pat. No. 5,118,910 entitled “Illuminated, Pressure-Actuated Switch” teaches a press-at-any-point type switch suitable for opening doors of a transit vehicle. The illumination is provided by a flexible, electro-luminescent planar lamp that is aligned with the actuation surface of the switch. The lamp receives power through electrical leads and provides continuous and constant illumination over the elongated actuation zone of the switch.
In some transit vehicle applications, it is required to maintain a continuous illumination of the switch but change color of such illumination when the door status changes from enabled to non enabled or vise versa. Generally, a green color light is used for enabled doors and a red color light is used for non-enabled doors. One disadvantage of the switch taught by U.S. Pat. No. 5,118,910 is that, as is well known, electro-luminescent planar lamps are capable of producing only one color. The second disadvantage is that an electro-luminescent planar lamp requires an inverter to convert the input electricity to the required AC electricity of the necessary frequency and voltage to operate the lamp. The third disadvantage is associated with the requirement for an external cover, particularly when subjected to the environmental elements such as moisture and dirt.
In transit vehicles which employ a contact-less sensing system for passenger detection, such as thought in U.S. Pat. No. 5,146,410, it is desirable to minimize the overall thickness of the switch devices in order to minimize protrusion of such device from the door surface and, more particularly, minimize unwanted echoes received by the sensors disposed within such contact-less sensing system.
As it can be seen from the above discussion, there is a need to provide an illuminated touch activated switch that overcomes the disadvantages of the presently used devices.